Portable barometer of the type invented by Jean-André de Luc. The instrument is enclosed in a wooden box with opening front. In transport, the mercury was moved to the longer arm of the barometric tube, where it was closed by means of a tap. The shorter tube is fitted with a small ivory cover. The barometric scales, drawn on paper, are in Paris inches. There is a plumb bob for checking verticality. The box also contains two mercury thermometers, with Fahrenheit and Réaumur thermometric scales, used to determine the barometric corrections made necessary by temperature variations. One of the two thermometers, designed to measure room temperature, can be removed from the box.